Optical transformer using curved strip waveguides to achieve a nearly unchanged F/number

Abstract

A transformer assembly particularly adapted, among other possible uses, for use in ring field illumination systems such as, for example, systems used in microlithography, said optical transformer assembly including an elongated member of glass or fused silica having a nearly circular or rectangular shape at one end for receiving a non-uniform input beam of light and through a gradual transitional intermediate section to an arcuate shape at the other end for outputting a uniformly illuminated arcuate shaped beam of light.

What is claimed is: 
     
       1. An optical transformer assembly comprising: an input section of glass or fused silica having a rectangular shape, said section having an input end for receiving a non-uniform input beam of light, said section having a length to width ratio sufficient to output substantially uniform irradiance;   a transitional intermediate section having four strips of glass or fused silica, said strips being fused together to form a mating rectangular shape at the end attached to the output of said input section and an arcuate shape at the other end, at a first transverse cross-section location of said intermediate section, said four strips being parallel with respect to each other with their ends disposed in stepped relationship, the side edges of each strip being fused to the side edge of the adjacent strip;   at a second transverse cross-section location of said intermediate section spaced from said first location toward the output of said intermediate section, said four strips being parallel with respect to each other with their ends disposed in stepped relationship, said steps being wider than the steps at said first cross-section location, the side edges of each strip being fused to the side edges of the adjacent strip;   at a third transverse cross-section location of said intermediate section spaced from said first and second locations toward the output of said intermediate section, the center two of said strips being fused in end to end relationship and the outside two of said strips being spaced from said center two strips;     an output section of glass or fused silica having a mating arcuate shape at the end attached to the output of said intermediate section, the output end of said output section having substantially the same arcuate shape as the input thereof, the length of said output section being sufficient to output substantially uniform irradiance; and   said optical transformer being fabricated from a single monolithic optical member which is substantially smooth, wrinkle free with parallel sides whereby the f/number from the input section to the output section is nearly unchanged.   
     
     
       2. An optical transformer assembly comprising: an input section of glass or fused silica having a substantially circular shaped input and a substantially rectangular shaped output, said input end serving to receive a non-uniform input beam of light, said section having a length to width ratio sufficient to output substantially uniform irradiance;   a transitional intermediate section having four strips of glass or fused silica, said strips being fused together to form a mating rectangular shape at the end attached to the output of said input section and an arcuate shape at the other end;   at a first transverse cross-section location of said intermediate section, said four strips being parallel with respect to each other with their ends disposed in stepped relationship, the side edges of each strip being fused to the side edge of the adjacent strip; at a second transverse cross-section location of said intermediate section spaced from said first location toward the output of said intermediate section, said four strips being parallel with respect to each other with their ends disposed in spaced relationship, said steps being wider than the steps at said first cross-section location, the side edges of each strip being fused to the side edges of the adjacent strip;   at a third transverse cross-section location of said intermediate section spaced from said first and second locations toward the output of said intermediate section, the center two of said strips being fused in end to end relationship and the outside two of said strips being spaced from said center two strips;     an output section of glass or fused silica having a mating arcuate shape at the end attached to the output of said intermediate section, the output end of said output section having substantially the same arcuate shape as the input thereof, the length of said output section being sufficient to output substantially uniformed irradiance; and   said optical transformer being fabricated from a single monolithic optical member which is substantially smooth, wrinkle free with parallel sides whereby the f/number from the input section to the output section is nearly unchanged.   
     
     
       3. An optical transformer assembly according to claim 1 further including a glass container for enclosing said optical transformer, the ends of said transformer being fused at the ends of said glass container. 
     
     
       4. An optical transformer assembly according to claim 2 further including a glass container for enclosing said optical transformer, the ends of said ransformer being fused to windows at the ends of said glass container.